Voiceover users can still access controls outside of the video player in full screen mode
Voiceover users can still access controls such as the back button, the name of the unit, previous and next unit buttons, etc. while the video player is in fullscreen mode. If the user interacts with any of these, either intentionally or not, the video continues to play and they have to someone navigate back to the video in order to get it to stop playing.
Only the controls visible on-screen, pertaining to video playback and control, should be accessible to the Voiceover user.